Several trends in the communications industry are contributing to make the efficient use of power a top issue in the design of network system components. As bridging, switching and routing systems increase in performance, their power requirements also increase. An increase in power adversely affects product features, such as cost and reliability. Costs are increased, for example, by the requirements of larger power supplies and fans. Reliability is compromised by the potential of hotter components. The power increase also adversely affects operating environment features by driving higher utility costs and higher installation and maintenance costs, such as building cooling, space needs and battery backup requirements. On the other hand, network system components which run cool provide many important benefits, including the ability to pack more ports into a smaller space and still stay within thermal operating limits, and the capability to stay online longer, perhaps with reduced capacity, in a battery back-up mode when main power fails.
Previously wired solutions for network communication are moving to wireless equipment for ease of use and mobility. Wireless devices abound today and will only increase in the future via analog and digital handheld phones, personal digital assistants (PDAs), laptops, subnotebooks, electronic books, etc. Most of these devices presently communicate or will communicate using wireless technologies, such as cellular, digital/PCS, 802.11, Bluetooth™, etc. Internet access is being enabled on most of these devices today or in the near future. New, data intensive features like web browsing and instant messaging are being added just as fast as improvements in low power hardware integration will allow. Network system components, such as network processors (NP) now used in powerful routing equipment today, may be used in small, mobile devices in the future provided that the technology is properly designed for low power applications.
The amount of power that a device uses often varies greatly between passive use (such as a cellular phone in standby mode or a laptop computer in sleep mode) and active use (such as placing a call on a cellular phone or running an application on a laptop computer). Power management features allow a device to conserve power using different operational modes, such as standby or sleep. In these types of power modes, most of a device can be powered off with the state saved, parts of the device can be powered off with allowance for a wake-up by another part of the device, or parts of the device can be run at lower power during periods of low usage. These power-conserving operational modes can be used to greatly increase the battery life of the device and the amount of time that the device can be in standby or can be used actively.
Due to the increasingly networked nature of wireless battery-powered devices (such as higher bandwidth requirements for multimedia and the addition of Internet support and applications), there is more of a need than ever to add networking assists or network processing functionality into these devices while leaving the General Purpose Processor (GPP) free to run applications. This drives the need for power-efficient network processors (NPs) and the use of power-saving techniques in the design of these network processors.
These same power-saving features can be used in wired devices for battery-backup modes when there is a loss of power. An example would be a small-office/home-office (SOHO) router which is used to provide voice lines to a residence using Voice over Packet or Voice over ATM (asynchronous transfer mode) technology. In the United States, such a device must provide eight hours of “talk” time and 24 hours of standby from a battery in case of a power failure to ensure 911 emergency support.
These features can also be used in wired devices just to save electricity, which lowers operational expenses and is environmentally friendly. The use of advanced power management techniques according to the present invention will also improve thermal characteristics for high density network processor applications in telco racks by reducing typical power requirements. Carrier companies are asking for higher port densities to handle rapidly increasing volumes of voice and data traffic. These same companies are very sensitive to increase in overhead expenses due to floor space requirements for network equipment racks. It is becoming increasingly important for network equipment manufacturers to pack more network traffic processing capability into smaller spaces. Hence, the network processors used in this network equipment need to become more power efficient.